linux/virt
Andrew Jones cde9af6e79 KVM: add explicit barrier to kvm_vcpu_kick
kvm_vcpu_kick() must issue a general memory barrier prior to reading
vcpu->mode in order to ensure correctness of the mutual-exclusion
memory barrier pattern used with vcpu->requests.  While the cmpxchg
called from kvm_vcpu_kick():

 kvm_vcpu_kick
   kvm_arch_vcpu_should_kick
     kvm_vcpu_exiting_guest_mode
       cmpxchg

implies general memory barriers before and after the operation, that
implication is only valid when cmpxchg succeeds.  We need an explicit
barrier for when it fails, otherwise a VCPU thread on its entry path
that reads zero for vcpu->requests does not exclude the possibility
the requesting thread sees !IN_GUEST_MODE when it reads vcpu->mode.

kvm_make_all_cpus_request already had a barrier, so we remove it, as
now it would be redundant.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-04-27 14:16:17 +02:00
..
kvm KVM: add explicit barrier to kvm_vcpu_kick 2017-04-27 14:16:17 +02:00
lib KVM: eventfd: fix NULL deref irqbypass consumer 2017-01-12 14:42:34 +01:00
Makefile virt: Add virt directory to the top Makefile 2015-10-01 15:06:44 +02:00